Loosening of a maxillary complete denture during yawning is most likely due to interference with which anatomical structure?

The loosening of a maxillary complete denture during yawning is most commonly associated with the coronoid process. When a patient yawns, the movement of the mandible can bring the coronoid process into contact with the posterior aspect of the maxillary denture. Since the coronoid process is a prominent anatomical structure, it can exert pressure on the denture if there is insufficient space or if the denture extends too far back. This can disrupt the stability of the denture and lead to loosening.

Considering the other anatomical structures mentioned, the hamular notch is important in providing support and retention for the posterior aspect of the maxillary denture but does not directly impact stability during jaw movements like yawning. The vibrating line is the region observed with the movement of the soft palate and is significant for identifying the border of the denture but is not involved in loosening during yawning. The masseter muscle, while an important muscle for mastication, does not interfere with the fit of the complete denture during the yawning motion. Therefore, the primary anatomical structure contributing to the loosening of the maxillary complete denture during yawning is indeed the coronoid process.